This question has been answered REPEATEDLY. ER is MUCH more involved to prove safety and efficacy. IR= Quick & Easy, ER= Long & difficult. And which ER would he do? Oxy/Naltrexone ER was not possible because Pfizer's exclusivity. Morphine/Naltrexone ER was already a failure. I suggested several times that Dilaudid/Naltrexone ER would be a unique and interesting product, but that would have required substantially more time & money than Oxy IR.